In contrast to previous Scala version, it is no longer allowed to have arbitrary regular expressions, for the reasons described below.

General RegExp patterns temporarily retracted from Scala

Since we discovered a problem in correctness, this feature is temporarily retracted from the Scala language. If there is request from the user community, we might reactivate it in an improved form.

According to our opinion regular expressions patterns were not so useful for XML processing as we estimated. In real life XML processing applications, XPath seems a far better option. When we discovered that our translation or regular expressions patterns has some bugs for esoteric patterns which are unusual yet hard to exclude, we chose it would be time to simplify the language.